_NATURE ENVIRONMENT Entomology

_The Pioneers of Poop

You’ve probably heard about fecal transplants, the latest way for humans to get benevolent bacteria into their intestines. But a group of ants may have been the original poop pill pioneers — 46 million years ago.

_Jacob Russell

Russell is an associate professor in the College of Arts and Sciences.

Turtle ants (Cephalotes) are able to supplement their low-nitrogen diets by passing helpful bacteria from older ants to younger ones through anal secretions. Once this is done, the bacteria naturally produce the nitrogen necessary for turtle ants to survive, according to a collaborative study in Nature Communications.

“Turtle ants eat a lot of food that is hard to digest and contains few essential nutrients in accessible form,” says Jacob Russell, an associate professor in Drexel’s College of Arts and Sciences and the paper’s senior author. “The fact that they can subsist on such diets and have moved away from aggressively competing for more optimal food resources with other ants is almost certainly a function of their investment in symbioses with gut bacteria.”

This multi-institution, international study was spearheaded by Yi Hu, while finishing a postdoc at Drexel, and Jon Sanders, a postdoc at the University of California in San Diego.

The study was inspired by work Russell did with other researchers more than a decade ago when they discovered that many ants with low-quality diets harbored specialized bacterial symbionts – likely to supplement their diets.

It turned out that turtle ants are a great example of this. To test whether the gut bacteria contributed to the ants’ nutrient intake, the researchers kept some turtle ants in a lab, put them on a diet of urea (the main waste in urine), and gave them antibiotics — which killed their gut bacteria. In this case, the ants weren’t able to get the nitrogen they normally did when on a diet strictly made up of urea.

Finding that turtle ants keep nitrogen-producing bacteria in their guts shows how they can survive while eating foods that few other animals want.

Mammals, like us, also have a complex set of bacteria in our guts that may have also evolved with hosts for millions of years.

“The turtle ant system — which is relatively simple — may prove useful in helping us to model questions about our own partnerships with microbes and how important they are for human health,” Russell concludes.